Electrochemical cells, such as polymer electrolyte electrochemical cells, have been extensively studied in fields of a fuel cell, water electrolysis, and the like.
Among these electrochemical cells, e.g., a fuel cell is a system in which a fuel such as hydrogen is electrochemically reacted with an oxidant such as oxygen to generate electric power. Among them, a polymer electrolyte fuel cell (PEFC) can operate at low temperatures as compared with other fuel cells and its reaction product is water, thereby lowering an environmental load. Hence this cell has been developed and supplied to practical use as a household stationary power source, and further as an automotive power source. Such a polymer electrolyte fuel cell is provided with a membrane electrode assembly (MEA) basically including a polyelectrolyte membrane having proton conductivity and two electrodes, i.e., a fuel electrode (anode) to be supplied with hydrogen and an air electrode (cathode) to be supplied with air, which sandwich in the membrane therebetween.
For a catalyst layer of each electrode used in the polymer electrolyte fuel cell, a carbon-supported catalyst is typically employed to control pores in the catalyst layer and to suppress catalyst agglomeration.
A slurry method, a sputtering method, or a vapor deposition method has been studied to provide the catalyst layer.